I don't think I'd seen a hamburger menu rendered on a list, for each item, before. Normally a "hamburger menu" appears once, probably at the top of the page, in some kind of navigation bar. In that context, that icon definitely reads "drag to re-order list item" to me.

We have found that people are afraid to mess things up, and don’t know what three lines means, so never click them. A lot more than you would think.

Everyone sees the hamburger icon for the first time. It certainly isn't obvious what it means. You need to decide what is more important, that your site look contemporary or that your users can find the information/product/service they are looking for.

https://www.nngroup.com/articles/hamburger-menus/

Hamburger menu icons usually have a fixed position and are part of a header or something of that sort. Floating lines like that would always read as "drag grip" to me.

This is the case for many people. Another explanation is that he was being empathetic.

As a designer himself, he probably tries to approach design examinations from many different perspectives (we do this at work with new designs: if I was an 70 year old woman, what would I see here?) to find edge cases where the design doesn't work.